1. Field of the Invention
The present invention relates to a gas insulated switching device transforming an electrical energy in a power system, particularly to installation of a current transformer.
2. Discussion of Background
A gas insulated switching device, used in a field of generating and transforming an electric power in a power system, is constructed by a switching device, a conductor, a current transformer, a surging arrester, and so on, which are accommodated in a metallic pressure container, filled with an arc-extinguishing gas such as a sulfur hexafluoride (hereinbelow referred to as SF6 gas) having excellent insulating capability and excellent arc-extinguishing capability, and these switching device, the conductor, the current transformer, the surging arrester, and so on are mutually connected, whereby the gas insulated switching device has been small-sized. However, further improvement in economy is required by reducing a space occupied by the gas insulated switching device by virtue of miniaturization and improvement in reliability of component obtained as a result of a recent technology development.
FIG. 7 is a cross-sectional view illustrating a conventional current transformer. In FIG. 7, numerical references 1, 4 designate a pressure container, in which a conductor 2 is accommodated in a center thereof and an SF6 gas is filled. Numerical reference 3 designates an insulating spacer for supporting the conductor 2 and separating the gas in the pressure container 1 from the gas in the other pressure container 4, connected to a pressure container 1. Numerical reference 6 designates a current transformer holder attached to flanges of the pressure containers 1 and 4 via an insulating spacer 3, the current transformer holder includes a cylindrical portion having grooves like a ring and an attaching flange corresponding to the flanges of the pressure containers 1 and 4. Numerical reference 7 designates a plurality of Rogowskii coils, positioned in the groove like the ring in the current transformer holder 6 via a spacer 8 in an axial direction of the pressure container 1. Numerical reference 9 designates a fixing plate for fixing the Rogowskii coils 7 inside the groove. A current transforming portion is constructed by the current transformer holder 6, the Rogowskii coils 7, the spacer 8, and the fixing plate 9 for detecting a current applied to the conductor 2. The Rogowskii coils 7 is formed by uniformly wind a coil around a high molecular member, being flexible and having a circular cross sectional view or the like by many turns, wherein the Rogowskii coils work as a current sensor, from which a current signal is obtainable in proportion to a current value, flowing inside the Rogowskii coils 7.
However, since the Rogowskii coils 7 forming the current transformer are flexible, hollow portions of the Rogowskii coils are deformed by a pressure applied to surfaces of the Rogowskii coils at time of attaching these to the current transformer holder 6, whereby an accuracy of detecting a current is deteriorated.
Further, since the Rogowskii coils 7 are attached to the current transformer holder 6 having protrusions in the axial directions of the pressure container 1, for example, in case that a breaker container containing a breaker and so on are connected, the protrusion of the current transformer holder 6 insufficiently protrudes inside the breaker container, whereby the length of the pressure container 1 should be increased, and a miniaturization of an entirety of the switching device is difficult.
Further, although it is necessary to sufficiently keep an insulating distance between the Rogowskii coils and the conductor 2, the current transformer holder 6 also protrudes in a radial direction of the pressure container 1, whereby the diameter of the pressure container is increased, miniaturization of the entire switching device is difficult.
It is an object of the present invention to solve the above-mentioned problems inherent in the conventional technique and to provide a gas insulated switching device, in which a highly accurate current transformer is equipped for miniaturizing the gas insulated switching device.
According to a first aspect of the present invention, there is provided a gas insulated switching device comprising a mutually connected series of containers having a conductor in a center and filled with an insulating and arc-extinguishing gas around the conductor; and a current transformer including Rogowskii coils for detecting a current flowing through the conductor, the current transformer is attached to a flange of the pressure containers through an annular metallic adaptor, wherein the current transformer is accommodated in grooves formed toward an inside of a metallic adaptor and uses the metallic adaptor to obtain an earth potential.
According to a second aspect of the present invention, there is provided a gas insulated switching device, wherein the Rogowskii coils of the current transformer is formed by uniformly winding a coil around an inflexible insulating member by many turns.
According to a third aspect of the present invention, there is provided a gas insulated switching device, wherein the metallic adaptor is attached via an insulating spacer for separating the gas in the mutually connected series containers, and a rounded portion is formed on an inner peripheral surface on a side, being in contact with the insulating spacer for relaxing an electric field in a triple junction among the insulating and arc-extinguishing gas filled in the pressure containers, the insulating spacer, and the metallic adaptor.
According to a fourth aspect of the present invention, there is provided a gas insulated switching device, wherein a flange of the pressure containers is the metallic adaptor.
According to a fifth aspect of the present invention, there is provided a gas insulated switching device, wherein a current detector for measuring the current, detected by the current converter, is located on an outer periphery of the metallic adaptor.
According to a sixth aspect of the present invention, there is provided a gas insulated switching device, wherein the current transformer includes Rogowskii coils for detecting a current passing through the conductor, which are attached to a breaker in a breaker container being adjacent to and connected to the series of pressure containers through an angular metallic adaptor located in an outer periphery of the conductor connected to the breaker, and the current transformer is accommodated in a groove formed in the metallic adaptor toward an inside thereof, and uses the metallic adaptor to obtain an earth potential.
According to a seventh aspect of the present invention, there is provided the gas insulated switching device, wherein a plurality of Rogowskii coils having same dimensions are arranged side by side in the metallic adaptor in an axial direction of the pressure containers around a common axis center of the Rogowskii coils.
According to an eighth aspect a gas insulated switching device according to the present invention is that a plurality of Rogowskii coils having same dimensions in an axial direction of a cross section of the coils and different dimensions in radial directions of the coils are arranged in radial directions of the pressure containers so as to be concentrically piled up.
According to a ninth aspect of the present invention, there is provided a gas insulated switching device wherein the Rogowskii coils is attached to the metallic adaptor by monolithically molding with a flexible resin inside the metallic adaptor.